What muscles are involved in the action of retrusion?

The correct answer identifies the muscles primarily responsible for the action of retrusion, which refers to moving the jaw backward. The posterior fibers of the temporalis muscle are particularly important for this action, as they contract to pull the mandible backward. Additionally, the anterior portion of the digastric muscle assists in stabilizing the mandible during this movement.

This combination of muscles effectively facilitates the retrusion movement, which is crucial for various functional activities such as chewing and speaking. In contrast, other muscles listed do not primarily contribute to the retrusion action; for instance, while the medial pterygoid and the masseter are involved in different movements (like elevation and protraction of the jaw), they are not the main contributors to retracting the jaw.